In many manufacturing processes that involve multiple processing steps or stages such as in steel manufacturing and chemical products manufacture, the quality of a product that is manufactured is only discovered at the end of the manufacturing process. The product quality such as the degree of defect, however, is often influenced by processing conditions during upstream or early processing stages. Despite those processing conditions which may be present during the upstream processing stages, there is no easy way of uncovering early indicators that could remediate the product quality problems.
Known quality control methods may apply a conventional process quality control system to a processing stage with pre-determined control bounds, which operates on each processing stage independently. An example of a conventional process quality control system is statistical process control (SPC). Integrating independent operations of different processing stages in identifying product quality indicators or product quality control mechanisms has been a challenge in multi-stage manufacturing processes.